In the typical foudrinier papermaking machine, an aqueous suspension of fibers, called the "furnish" is flowed onto a traveling fourdrinier wire or medium, generally a woven belt of wire and/or synthetic material, to form a continuous sheet of paper or paper-like material. In this connection, the expression "paper or paper-like material" is used in a broad or generic sense and is intended to include such items as paper, kraft, board, pulp, plastic, asbestos sheet and other non-woven sheet-like structures. As the "furnish" travels along on the fourdrinier wire, much of its water content is removed by draining and a somewhat self-supporting continuous web is formed. This water removal is enhanced by the use of such well-known devices as hydrofoils, table rolls, and/or suction devices.
After leaving the forming section at the couch roll, the somewhat self-supporting web is transferred to a press section in the machine where still more of its water content is removed by passing it through a series of pressure nips formed by cooperating press rolls, these press rolls also serving to compact the web as well. The paper web is then transferred to a dryer section in the machine where it is passed about and held in heat transfer relationship with a series of heated, cylindrical rolls by which still further amounts of water are removed by evaporation. Finally, the paper web is passed through a series of calender rolls where loose fiber ends are laid down and the paper web is provided with a smooth finish, after which the paper web is collected on a suitable reel.
The present invention relates to a hydrofoil unit which comprises a hydrofoil blade support member and a plurality of spaced hydrofoil blades supported thereby. A hydrofoil blade is a stationary blade-like structure positioned beneath the forming medium in supporting relationship thereto. The functions of the hydrofoil blade include extracting water from the furnish to obtain a self-supporting web having the desired consistency and otherwise assuring proper formation of such web. The word "formation" is used herein to describe the interlocking of individual fibers to form networks or combinations of such individual fibers which are further matted together with other networks of fibers and collectively allow for the retention of various fines and fillers used in the papermaking process in producing the wet paper web. The present invention is directed to the function of paper web formation rather than dewatering per se and to this end is directed to controlling turbulence incurred in the forming section of the papermaking machine by providing a hydrofoil blade support member which allows for appropriate positioning of its associated hydrofoil blades.
In producing paper upon a fourdrinier papermaking machine the furnish is fed upon a moving forming medium which carries the paper web past various dewatering devices including hydrofoil units to remove water from the web. Such hydrofoil units include hydrofoil bodies which extend under the forming medium in the cross machine direction; that is, in a direction substantially at a right angle to the machine direction which is the direction in which the forming medium travels during the papermaking operation. Each hydrofoil body is generally supported upon support rails which extend in such machine direction along each side of the papermaking machine. Each hydrofoil body may support one or more hydrofoil blades and may be positioned along the support rails as desired allowing the user to be selective as to the area or areas to be dewatered during the papermaking process. In such hydrofoil units, although the hydrofoil body may be moved along the support rails, each hydrofoil blade is fixed relative to the hydrofoil body to which it is attached to the extent that each blade may not be moved in the machine direction relative to its supporting hydrofoil body or any other hydrofoil blades attached to such hydrofoil body, and in this connection reference is made to the following: Dunlap U.S. Pat. No. 3,027,941; Reynolds et al. U.S. Pat. Nos. 3,515,636 and 3,535,201; Gedemer et al. U.S. Pat. No. 3,576,715; Truxa U.S. Pat. No. 3,711,368; and, Boindetti U.S. Pat. No. 4,061,532. The dewatering capabilities of hydrofoil blades are well known in the art, and in this connection reference is made to Wrist U.S. Pat. No. 2,928,465, Burkhard et al. U.S. Pat. No. 2,928,466 and Thorp U.S. Pat. No. 3,432,385.
As the furnish is carried past the hydrofoil blades the furnish is continually in motion as a result of the movement of the forming medium and the forces exerted upon the furnish by the blades. Such motion is turbulent in that the individual particles of the furnish and/or the groupings of a plurality of such particles which have come together to form networks are moving in a highly irregular and rapidly fluctuating manner. During this phase of the papermaking process such continued agitation of the furnish has a significant affect upon the characteristics of the web being formed. Although it is believed that some turbulent motion is necessary to properly deflocculate the constituent fibers which comprise the furnish, it would be desirable to be able to control the degree of such motion in order to eliminate any deleterious characteristics which may result from too much or too little turbulent activity. In controlling turbulence it would be desirable to be able to control the intensity or force of the turbulence, its scale or size as well as the rate of decay or diminution thereof and to selectively control the rate or frequency of phase change of machine direction oriented furnish ridges. It is believed that such control of turbulence will significantly add to the control of flocculation of the fibers which form the furnish and thereby significantly affect the ability to control the nature of the paper web produced during the critical formative stages as the furnish travels through the forming section of the papermaking machine.
Accordingly, it is an object of this invention to provide a means whereby turbulence of the furnish in the forming section of the papermaking machine may be controlled.
Another object of this invention is to provide a means whereby turbulence of the furnish may be selectively controlled during the papermaking operation.
Yet another object of this invention is to provide a means to deflocculate as desired the constituent fibers which comprise the furnish.
Still another object of this invention is to provide a means whereby the appropriate utilization of hydrofoil units may be effected to assure that the furnish is not subjected to too much or too little turbulent activity as the wet paper web is carried upon the forming medium past hydrofoil blades.
A further object of this invention is to provide a means whereby turbulence of the furnish in the forming section of the papermaking machine may be controlled by selectively controlling the rate of frequency of phase change of machine direction oriented furnish ridges.